Spectroscopy, and specifically near infrared (NIR) spectroscopy, has been proposed as a technique for process monitoring in the manufacture of substances, such as pharmaceutical products. For example, in drying applications, e.g., pill drying, the spectroscopy instruments can be used to monitor the water or solvent content during the drying process. This allows the process to be terminated at the optimal time, saving energy and ensuring product uniformity between batches. In blending applications, spectroscopy can be used to monitor the distribution of the active ingredient in the binder material to insure that the processed material is completely admixed and thereafter terminate the blending process.